With regard to a third generation in mobile communication systems (Long Term Evolution (LTE), Beyond3G), stable service capable of both voice communication and high-speed data communication is being provided. In the future, as the transition from the voice communication to the data communication further progresses, high-speed communication having a throughput of current wired communication will be required.
Meanwhile, although the third generation system realizes highly flexible functions and services, the device cost tends to increase. There is also a problem in that an investment of an operator and a device development vendor is increasing.
Based on the above-described circumstances, in the next generation system, techniques not only for achieving high performance but also for simplifying functions of nodes constituting a system are being discussed in view of cost performance.
A configuration of the third generation system for integrating the function of a radio base station (NodeB) and the function of a radio network controller (RNC) which controls the radio base station, to realize a single node (accommodated in the radio base station) is being discussed. Therefore, the radio base station is required to autonomously perform management and control in the network.
The mobile communication system includes a host station (a radio network controller) which controls transmission power of a base station (a radio base station), and the host station controls the transmission power of the base station.
For example, the host station controls the transmission power to satisfy a target value (hereinafter, referred to as “control target value”) of communication quality for a mobile station with which each base station is communicating. The host station controls each of the base stations based on a report from each of the base stations to prevent the control target value from being remarkably unbalanced between the base stations or to prevent a control target value exceeding the total transmission power range of the base station from being set (for example, see Patent Document 1).
Meanwhile, in the next generation system, it is necessary for a function of the host station to be integrated into the base station, and for the base station to execute the above-described control operation autonomously. Generally, as methods of autonomously performing a control operation in a node (corresponding to the base station) that constitutes a network, the following methods (1) to (3) have been known: (1) a method of performing control such that a previously determined (fixed) target value is set for each control parameter, and all nodes (base stations) satisfy the target value; (2) a method of performing control through a virtual host station which is set by having an arbitrary node (base station) to function as the host station; and (3) a method of performing mutual monitoring and control between nodes (base stations).
However, in the above-described mobile communication system, in the case of method (1), there is little flexibility for growth or change of the network. Particularly, when the number of the mobile stations connected with the base station dynamically changes or installation environments of the base stations are individually different depending on a district or an operation environment as in the mobile communication system, it may be impossible for practical use.
Further, in the above-described mobile communication system, in the case of method (2), a load may be concentrated on the base station serving as the virtual host station, and a load balance with other base stations may be lost, thereby influencing or inducing failure on an original function as the base station.
Further, in the above-described mobile communication system, in the case of the method (3), it is difficult to optimize a relationship between nodes which perform mutual monitoring, and if a mutual relationship is improperly set, control is biased in one direction. For example, if all of the base stations increase the transmission power, an upper limit of the total transmission power may be finally reached, leading to network failure.
A technique disclosed in Patent Document 1 has the same problems as in the cases of the methods (1) to (3) if the function of the host station is integrated into the base station.    Patent Document 1: Japanese Unexamined Patent Publication, First Publication No. 2006-311459